Neutralization process

ABSTRACT

This invention relates to a process for neutralizing detergent acid mixes containing unreacted sulfating agent such as sulfuric acid with an alkaline component such as sodium hydroxide. The neutralization process is highly exothermic and contains as a by-product large amounts of sodium sulfate. Due to the exothermic nature of the reaction it is necessary to use heat exchangers to regulate the temperature of the reaction mass following the addition of the alkaline component. When the sodium sulfate is supersaturated in the reaction mass, it has been observed that sulfate salts buildup upon the surfaces of the heat exchanger and eventually the system must be shut down to remove the buildup. This invention is therefore directed to a continuous neutralization and heat exchange process wherein the downtime required for removal of the sulfate salts from the heat exchanger surfaces is effectively eliminated.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention described herein relates to a process for formingsurfactants for use in detergent compositions where a step in a processincludes cooling the reaction mass, following the mixture of an alkalinecomponent, the detergent acids and excess sulfating agent.

2. Discussion of the Art

The use of anionic surfactants particularly those where the anioniccharacter is caused by a sulfonate or a sulfate group is well known inthe detergency arts. Further, the sulfation or sulfonation of precursormaterials such as alkylbenzene to form alkylbenzene sulfonic acid whichis subsequently neutralized to the sulfonate is also well known in theart. For instance, U.S. Pat. No. 3,024,258, issued to Brooks et al, Mar.6, 1962, discloses a process for sulfonating a reactant continuously andrapidly as well as for separating the resulting sulfonated reactant fromthe excess sulfonating agent and to the continuous neutralization of theresulting detergent acids. During the neutralization step the Brooks etal patent describes cycling the neutralized product through a heatexchanger to maintain the temperature in the range of from 85° F. to140° F. The examples of Brooks et al indicate that the final productcontains sodium sulfate in water in a ratio of from about 1:11. TheBrooks et al patent is herein incorpated by reference.

Similarly, other patents describing sulfonation and sulfation processesare U.S. Pat. No. 3,259,645 issued July 5, 1966, U.S. Pat. No. 3,363,994issued Jan. 16, 1968, U.S. Pat. No. 3,350,428 issued Oct. 31, 1967, andU.S. Pat. No. 3,427, 342 issued Feb. 11, 1969, all to Brooks et al whichare herein incorporated by reference. Earlier patents describingsulfonation processes include U.S. Pat. No. 2,129,826, Reilly issuedSept. 13, 1938 and U.S. Pat. No. 2,039,989, issued to Gressner May 5,1936, both of which are herein incorporated by reference.

In the process of forming anionic surfactants which have a sulfuric orsulfonic acid moiety it is necessary to react a precursor with asulfating agent which is a material such as sulfur trioxide to form theorganic sulfuric or sulfonic acid. Materials which supply a source ofsulfur trioxide for the forming of such detergent acids are known assulfating agents and the term embraces sulfonating agents as well.Sulfating agents include pure sulfur trioxide or sulfur trioxide dilutedwith a gas which is inert in the reaction, such as hydrogen chloride orsulfur dioxide. The most common sulfating agent, however, is oleum whichis a mixture of sulfur trioxide dissolved or suspended in sulfuric acid.The method of formation of the detergent acids, also known as the acidmix, is not material to the present invention up to the point that anexcess of the sulfating agent should be present in addition to thatwhich is required to react the detergent precursor to the desired degreeof sulfation.

The reason for using an excess of the sulfating agent is basically toensure that the detergent precursor which is a relatively expensivematerial will be completely reacted. That is, for ecological, productperformance and cost reasons, it is undesirable to leave unreactedalkylbenzene in the detergent product as it is relatively volatile andwill in the instance of spray-dried formulations be driven off uponheating.

The step following the reaction of the detergent precursor and thesulfating agent is that of neutralizing the mixture containing theorganic sulfuric or sulfonic acid. This mixture will also contain theexcess sulfating agent, and water which is either introduced with thereactants or formed during the sulfation reaction. This mixture is thenneutralized with an alkaline component such as sodium hydroxide orsodium carbonate or a similar material to form the sodium salt of theorganic sulfuric or sulfonic acid. The introduction of the alkalinecomponent, however, also neutralizes the excess sulfating agent to formsodium sulfate.

This second mixture referred to herein as the reaction mass thencontains the sodium salt of the organic sulfuric or sulfonic acid,sodium sulfate, water, and small amounts of the excess alkalinecomponent. As the sulfation reaction and the neutralization reaction areboth highly exothermic it is necessary to quench the heat of reaction toavoid bringing the reaction mass to boil as well as to avoid undesirablesecondary reactions which may take place. The most common method ofquenching any exothermic reaction is to pass the product of the reactionthrough one or more heat exchangers where excess thermal energy isremoved thus lowering the temperature of the product for furtherprocessing. It is noted, that the sulfation reaction mixture may bequenched through heat exchange prior to the neutralization reaction ifdesired although the present invention only relates to heat exchangefollowing the neutralization step.

The most commonly used heat exchangers for the preparation of detergentsare simply a large conduit through which the reaction mass passes and aseries of smaller conduits within the larger conduit through which thecooling medium flows. In operation the cooling medium is of coursemaintained at a temperature below that of the reaction mass which swirlsaround the smaller conduits. The thermal energy then flows through thewalls of the smaller conduits where the heat energy is transferred tothe cooling medium and removed from the system. Thus, the reaction massis cooled to a desirable temperature for further processing.

Known systems for the neutralization step have involved processing thereaction mass in diluted form in the presence of large volumes of water.The water is present in the reaction mass from the neutralization andfrom the alkaline component, e.g., a solution of caustic. Water may alsohave been added directly to the reaction mass to purposely dilute theheat generated by the reaction.

Obvious economic reasons dictate that the presence of a large volume ofwater in the reaction mass is undesirable. For instance, the waterpresent in the reaction mass must be removed if the end product is to besolid such as a spray-dried granule. Moreover, the presence of the waterin the reaction mass requires that storage or processing facilities havegreater volume than that required for a reaction mass with lower watercontent. Conversely, lowered water content in the reaction mass allowsgreater throughput of the final product with existing equipment.

It is also observed, aside from the advantages listed above, that otherprocessing goals can be achieved by lowering the water content of thereaction mass. For example, sodium sulfate in dry form is usually addedto the reaction mass following the heat exchange operation to aid in thepreparation of granular detergent compositions. If desired, however, inthe present invention the sodium sulfate may be formed in situ duringthe neutralization step by using excess sulfating agent over that whichis needed to accomplish sulfation of the organic precursor. The excesssulfating agent is then neutralized by the alkaline component to formsodium sulfate. In the case where oleum is used as the sulfating agentversus sodium sulfate to generate a source of sodium sulfate in theproduct a density and cost/availability advantage favor the use ofoleum. Cost and availability is of course a readily apparent advantagewhile the density factor allows equivalent storage facilities to hold agreater weight of oleum as opposed to dry sodium sulfate.

An additional advantage to lowering the water content of the reactionmass resides in the difference of incorporating wet versus dry silicatesinto the detergent compositions. Most detergent products require thepresence of alkali metal silicates to provide an anti-corrosion benefitto exposed washing machine surfaces as well as to provide non-gooeygranules, e.g., granules which cake or do not flow freely under humidconditions.

The silicates, as stated above, may be added to the crutcher mixcontaining the reaction mass as a wet or dry material. If the watercontent of the crutcher mix is low, as is obtained in the presentinvention, then a slurry of wet silicate may be added to the crutchermix. If the water content of the crutcher is already high from theaqueous reaction mass, then it is usually necessary to add dry silicateto reduce the crutcher water content to lower the drying load whenforming the crutcher mix into granules. Drying load as used above isdefined as the heat energy required to remove water in granulesformation. It is also observed that not withstanding the use of costlyenergy for drying the crutcher mix, that a point can be reached wherethe crutcher mix is too wet to be dried by conventional spray-dryingtowers such as those described in U.S. Pat. Nos. 3,629,951 and3,629,955, both issued to R. P. Davis et al on Dec. 28, 1971, which areherein incorporated by reference.

It is thus seen that reducing the water content of the reaction mass andsubsequently that of the crutcher mix is highly desirable. Toeffectively reduce the water content of the reaction mass it isnecessary that the sodium sulfate be supersatured in relation to thewater. This is not undesirable as the sodium sulfate cannot beeconomically removed in a continuous detergent making operation and inany event the sodium sulfate is a very desirable ingredient, especiallyin its ability to act as a structurant to avoid gooey granules aspreviously stated in the discussion concerning the function of thesilicate.

It has been observed, however, that when the reaction mass is passedthrough a heat exchanger with the sodium sulfate in a supersaturatedcondition that the heat exchanger immediately suffers a reduction inheat energy transfer capacity.

This loss of energy transfer capacity has been determined to be causedby the buildup of anhydrous sodium sulfate in the heat exchanger.Moreover, the loss of energy transfer capacity continues until the heatexchanger is completely plugged with the reaction mass. Thus, while itis extremely desirable to operate the detergent making process underconditions where the sodium sulfate is supersaturated in the reactionmass it has been impractical, if not effectively impossible, to do so.

The difficulty which the present invention alleviates is caused by thesodium sulfate which when supersaturated in the aqueous reaction massprecipitates on the surfaces of the smaller conduits in the heatexchanger and continues to precipitate until the entire heat exchangeris plugged with the precipitated sodium sulfate. At this point if thereis but a single heat exchanger the neutralization reaction as well asthe earlier sulfation reaction must be shutdown and the heat exchangertorn apart and cleaned or flushed with water to remove the precipitatedsodium sulfate.

Alternatively, the sulfation reaction can be allowed to continue toproceed along with the neutralization reaction, however, additionalcapital expense is then necessary to provide a parallel series of heatexchangers through which the neutralized reaction mass is allowed topass while the first heat exchanger has the sodium sulfate removed.Either alternative is quite costly and extremely undesirable.

A second alternative is to process the reaction mass with sufficientwater present so that the sodium sulfate never becomes saturated in thereaction mass. However, such processing requires large amounts of waterwhich, as previously discussed, is undesirable.

In view of the high degree of interest of operating heat exchangers athigh capacity when removing heat from a neutralized detergent acid mixthe following objects of the present invention are developed.

It is an object of the present invention to provide a method for rapidlyand economically removing heat from a neutralized detergent acid mix.

It is a further object of the present invention to prepare an aqueousmixture of supersaturated sodium sulfate and the sodium salt of anorganic sulfuric or sulfonic acid having as a processing step thecooling of the mixture in a heat exchanger while introducing a slurry ofanhydrous sodium sulfate into the reaction mass to reduce the depositionof sodium sulfate in the heat exchanger.

Throughout the specification and claims, percentages and ratios are byweight and temperatures are in degrees Centrigrade unless otherwiseindicated.

SUMMARY OF THE INVENTION

In the process of removing thermal energy from an aqueous mixture ofsodium sulfate and the sodium salt of an organic sulfuric or sulfonicacid or mixtures thereof the steps of:

(a) reacting the organic sulfuric or sulfonic acid and excess sulfatingagent with an alkaline component thereby forming a supersaturatedsolution with respect to the sodium sulfate; and,

(b) cooling the reaction mass formed in step (a) in a heat exchangerwhile introducing into the reaction mass a sufficient amount of anaqueous slurry of anhydrous sodium sulfate, to reduce the deposition ofsodium sulfate on the surfaces of the heat exchanger.

DETAILED DESCRIPTION OF THE INVENTION

The present invention as stated above relates to a method of removingthermal energy from an aqueous mixture of sodium sulfate and the sodiumsalt of an organic sulfuric or sulfonic acid, while avoiding buildup ofsodium sulfate in the heat exchanger.

In fact the present invention is advantageously utilized any time it isnecessary to remove thermal energy from a supersaturated solution ofsodium sulfate. Ordinarily sodium sulfate is prepared as a commercialproduct in the rayon making process where excess sulfuric acid isreacted with an alkaline component. Thus the present invention hasutility outside of the field of detergent products and the nondetergentrelated aspects of the invention are employed advantageously.

For detergent products the presence of the desired level of the sodiumsulfate in the end product is accomplished by over-using the sulfatingagent which is present to add the anionic moiety to the detergentprecursor and then neutralizing the excess sulfating agent.

For the purpose of this invention the term "detergent precursor"includes any material which following sulfation is capable ofneutralization to form a surface active agent. Examples of such surfaceactive agents are alkylbenzene sulfonates, alkyl ether sulfates, alkylsulfates, olefin sulfonates, paraffin sulfonates,alpha-sulfocarboxylates, alpha-sulfocarboxylate alkylates, and mixturesof the foregoing. Such surfactants are listed for purposes ofexemplification but the present invention is not limited to such surfaceactive agents. Other materials which may be sulfated or sulfonatedwithin the scope of the present invention, and embraced within the termof organic sulfuric or sulfonic acids, include toluene and benzenesulfonic acids as well as cumene sulfonic acids.

The term "sulfating agent" is interchangeable with "sulfonating agent",and examples of such materials are sulfuric acid, oleum, andchlorosulfonic acid, and sulfur trioxide. Oleum is defined as a materialwhich is a mixture of sulfuric acid and sulfur trioxide. Oleum is thepreferred sulfating agent of the present invention.

In practice the amount of the sulfating agent needed to completelysulfate the detergent precursor is greater than the actual amount ofsulfating agent which is needed on a stoichiometric basis. Convenientlythe actual amount of sulfating agent used is related to the spent acidstrength which is defined by the following equation: ##EQU1## where(excess SO₃) is the sulfur trioxide introduced to the reaction over andabove that used in the sulfation. This excess sulfur trioxide and thesulfuric acid present is subsequently neutralized to form sodiumsulfate. The quantity (H₂ O) is the water introduced into the system orwhich is present during the sulfation process. The percentage spent acidstrength is a measure of the available sulfur trioxide which may be usedfor sulfation or sulfonation. In other words, where the sulfur trioxidewould react on a one-to-one mole basis with the detergent precursor togive a sulfated product, the presence of water in the system will lowerthe amount of sulfur trioxide available for the sulfation of thedetergent precursor. Thus, it is desirable to minimize the amount ofwater present during the sulfation step. The spent acid strength, asmore fully described later, is preferably from about 90% to about 103%.

The second chemical reaction carried out in following the presentinvention is the formation of the supersaturated solution of sodiumsulfate. This reaction is accomplished by neutralizing the sulfateddetergent precursor and the unreacted sulfating agent with an alkalinecomponent. The alkaline component is any material which will function asa Lewis base, e.g., a material which will take up hydrogen ions to formwater. The most common alkaline components utilized in the presentinvention will be sodium hydroxide or sodium carbonate. Other suitablematerials, however, include potassium hydroxide, potassium carbonate,and partially neutralized salts such as bicarbonates andsesquicarbonates. The first aspect of the present invention set forth indetail is the sulfation system for forming the organic sulfuric orsulfonic acid from the detergent precursor.

The Sulfation System

Sulfation or sulfonation of various organic components, when carried outwith oleum or sulfuric acid, may be done on a continuous scale such asin a dominant bath system or on a single batch basis. For the purposesof the present invention, the benefits may be obtained either as singlebatch reaction or on a continuous process.

A. Batch System

The batch process is an operation comprising adding the sulfating agentand the organic detergent precursor which is to be sulfated orsulfonated into a vat.

The initial reaction in the batch process proceeds rapidly tocompleteness because of the high concentration of the reactants.However, the final concentration of the sulfated organic product in theacid mix will be lower because of the poor mixing encountered in thebatch process. The yield in a batch process can, however, be increasedby thoroughly mixing the system by any conventional means.

The product obtained from the batch process comprises the sulfatedreaction product as well as any excess sulfating agent and unreacteddetergent precursor. The resultant acid mix described above is thenfurther processed to remove the excess sulfating agent, or the acid mixmay be neutralized with the excess sulfating agent present. Preferably,the acid mix does not have the excess sulfating agent removed from itprior to neutralization, so that the sodium sulfate will be presentunder conditions of super-saturation in the reaction mass. The reactionmass also known as paste is transported by conventional means to theheat exchanger.

B. Dominant Bath

The dominant bath is the most commonly used oleum or sulfuric acidsulfation process. The dominant bath provides for a continuousproduction of an acid mix. In contrast to the batch process, thedominant bath allows the preparation of an acid mix under much morecontrolled reaction conditions.

In the dominant bath process the reactants are injected into arecirculating stream of reaction products. The heat of reaction which isconsiderable in a sulfation or sulfonation process is thus dissipatedinto the recirculating acid mix which facilitates heat removal andmixing. In an ideal dominant bath the reactants are completelydistributed throughout the system such that all parts of the bath havean identical composition with the mean reaction time equal to the volumeof the system divided by the effluent flow rate. In this contexteffluent is defined as the acid mix which is removed from the system tobe further processed, such as paste formation. In the dominant bathsystem the recirculation ratio will determine the degree of approach tothe ideal system. The recirculation ratio is defined as being the volumeof recirculated material divided by the volume of the effluent. Typicalrecirculation rates which will vary according to the material to besulfated are from 15:1 to 40:1 with an average of 25:1. Thus, arecirculation ratio of 25:1 indicates that for every part of effluent,25 parts of acid mix are recirculated through the system. Therecirculation ratio also indicates the maximum amount of new reactantswhich may enter the system; thus the rate at which the effluent leavesthe system is equal to the rate at which the new reactants enter thesystem.

In contrast to a batch system where the reaction is initially fast asthe reactants are high in concentration with the rate decreasing as thereactants are consumed the dominant bath provides a system where thereactants are at their final concentration and hence the reaction isrelatively slower. The longer reaction time for completion of thesulfation reaction is the most notable disadvantage of the dominant bathsystem. The foregoing disadvantage however, is greatly outweighed by theheat removal capacity in the dominant bath resulting in less charredmaterial.

To avoid using a dominant bath with an unduly large volume or greatlyincreasing the recirculation ratio, it has been suggested to remove theeffluent acid mix from the system before the sulfation reaction has beencompleted. The effluent which has been substantially reacted is thenpassed through a coil of sufficient length to allow the sulfationreaction to continue to completion despite the absence of mixing. Theuse of the coil is possible because the effluent has been substantiallyreacted in the dominant bath, thus requiring little or no heat transferin the reaction coil. The length of the coil and the recirculation ratiocan thus be varied so that the various sulfatable materials can achievemaximum completeness of the reaction with the shortest period of time inthe dominant bath and in the coil.

If two components are to be sulfated which require different spent acidstrengths for completeness and quality, series sulfation in the dominantbath may be employed. Series sulfation is a system in which onecomponent is first sulfated as has been previously discussed, and thenthat acid mix is used as a diluent for the sulfation of a secondmaterial. A common practice is to sulfonate an alkylbenzene first andthen combine the acid mix with a fatty alcohol or an ethoxylated alcoholprior to sulfating the latter materials.

The acid mix, following either of the procedures described above is thenconverted to the paste or reaction mass as indicated under theneutralization discussion, supra.

C. Film Sulfonation

Many detergent precursors can be sulfated by using film sulfationmethods. Basically the process in a film reactor comprises introducingthe detergent precursor at the top of a reaction vessel such that a thinfilm is formed on the walls of the vessel. The film is continuouslyexposed to a gaseous sulfating agent as the film moves along the surfaceof the reaction vessel. The sulfating agent may be sulfur trioxide orsulfur trioxide diluted with a gas which is inert in the process such assulfur dioxide.

Examples of suitable detergent precursors which may be sulfated in thefilm process are ethoxylated alcohols, alpha-olefins and aliphaticcarboxylic acids. Further film reactor techniques are described in U.S.Pat. Nos. 3,346,505; 3,309,392; 3,531,518; and 3,535,339 hereinincorporated by reference.

D. Sulfating Agent

As was previously stated in this application the term "sulfating agent"is to be used in its generic sense indicating a material which iscapable of sulfating or sulfonating another compound. The sulfatingagents with which the present invention is primarily concerned aresulfuric acid, oleum, chlorosulfonic acid or sulfur trioxide. Thepractical use of sulfuric acid as a sulfating agent is limited to thosesituations where 100% sulfuric acid is used, as the spent acid strengthis otherwise too low to ensure sulfation of the detergent precursor.Chlorosulfonic acid is normally employed in a batch reaction whilesulfur trioxide diluted with an inert gas is employed in a film reactor.

Oleum, which is a mixture of sulfuric acid and sulfur trioxide, is thepreferred sulfating agent in the present invention when the sulfation iscarried out in a batch process or in a dominant bath system. The acidstrength of the oleum used may be as high as 65%; however, the preferredrange of oleum acid strengths is between 10% and 40%. Acid strength isdefined as the percentage of a mixture of sulfur trioxide and sulfuricacid which is sulfur trioxide. Thus, a 10% acid strength is 10 partssulfur trioxide and 90 parts sulfuric acid.

The choice of the oleum strength used is dependent upon such factors asthe desired degree of completeness of sulfation in the dominant bath,the limitations on heat exchanger capacity wherein higher concentrationsof oleum result in substantially higher reaction temperatures, thedegree of charring which can be tolerated and the choice of the materialto be sulfated.

The particular materials of interest in the instant invention arealkylbenzenes, fatty alcohols and ethoxylated alcohols, although otherdetergent precursors are utilized in the instant invention such asalpha-olefins, fatty acids, and fatty acid esters or other sulfatableorganic compounds.

As used herein the term, "sulfatable compound", is the material whichwhen reacted with the sulfating agent will form the organic sulfuric, orsulfonic acid.

An alkylbenzene which may include some branched chain material in thealkyl group will preferentially sulfonate with sulfuric acid or oleum inthe para position with minor amounts of sulfonation at other positionson the benzene ring. The sulfonation of the alkylbenzene is anonreversible reaction; however, the presence of water in the system mayreduce the spent acid strength to a point at which the sulfonationreaction does not proceed. Below a spent acid strength of about 90% thesulfonation reaction will not proceed while at spent acid concentrationsabove 100%, secondary reactions which affect the color of theneutralized paste and odor become troublesome. Spent acid concentrationsmay be from 95% to 103%, preferably in the 98.0-101% range for the bestcompleteness of alkylbenzene sulfonation with acceptable charring. Thesecondary reactions which are alluded to above can include oxidation,dehydration, and rearrangement of the alkyl radical of the alkylbenzene.The apparent acid strength of the oleum used with an alkylbenzene shouldbe from about 100% to abou 122.5%, preferably about 102% to about122.5%. Apparent acid strength is defined as the amount of sulfuric acidwhich can be formed from oleum if all the sulfur trioxide is convertedto sulfuric acid. Thus, by convention, a mixture of 30 parts sulfurtrioxide and 70 parts sulfuric acid has an apparent acid strength of106.75%.

The sulfonation of an alkylbenzene is preferably carried out in adominant bath with a temperature maintained between 29° C. and 65° C.,preferably from 43° C. to 55° C., with a recirculation ratio of greaterthan 15:1 and preferably greater than 25:1. The weight ratio ofalkylbenzene to sulfating agent is from about 1:8 to 7:1, preferablyabout 1:4 to 10:3. Alkyl chains on an alkylbenzene contain from about 9to 15 carbon atoms, preferably between 11 and 12 carbon atoms.

The sulfation reaction of a fatty alcohol, preferably having 10 to 20carbon atoms, proceeds rapidly but is reversible in the presence ofwater. Fatty alcohols while undergoing sulfation are also prone to sidereactions resulting in the formation of alkenes, ethers, esters, andaldehydes. A high spent acid strength minimizes the reversiblehydrolysis but increases the dehydration and oxidation reactions notedabove.

The temperature range at which sulfation of an alcohol is bestaccomplished in a dominant bath system is between 29° C. and 65° C., andpreferably from 38° C. to 52° C. with a recirculation ratio of greaterthan 15:1 and preferably greater than 25:1. The apparent acid strengthused in sulfating a fatty alcohol should be from about 100% to about122.5%, preferably about 102% to about 122.5%. The spent acid strengthis preferably maintained in the range of from about 90% to about 103%and preferably from about 95% to about 101%. The weight ratio ofsulfating agent to fatty alcohol is from about 3:1 to about 1:4,preferably about 2:1 to about 1:2. Preferably the fatty alcohol containsfrom about 8 to 24 carbon atoms with especially useful materials beingof the tallow length.

The sulfation of an ethoxylated alcohol may be carried out by oleum orsulfuric acid in either a batch, the dominant bath process, or by filmsulfation.

The apparent acid strength used in sulfating an ethoxylated alcoholshould be from about 100% to about 122.5%, preferably about 102% toabout 122.5%. The sulfation of the ethoxylated alcohol may take placebetween about 29° C. and about 65° C. and preferably from about 40° C.to about 55° C. The percentage of spent acid strength resulting from thepreparation of an alkyl ether sulfuric acid should be maintained betweenabout 90% and about 103%, and preferably from about 95% to about 101%with a recirculation ratio of greater than 15:1, preferably greater than25:1. The weight ratio of sulfating agent to ethoxylated alcohol is fromabout 7:1 to about 1:10, preferably about 3:1 to about 1:3.

The ethoxylated alcohol preferably has an alkyl radical with from 8 to24 carbon atoms and from 1 to 30 ethoxy groups. A preferred detergentprecursor is the ethoxylated alcohol with an alkyl chain length averagevarying between 12 and 16 carbon atoms and the average degree ofethoxylation of said mixture varying between 1 and 4 moles of ethyleneoxide, said mixture comprising:

(a) from about 0% to 10% by weight of said ethoxylated alcohol mixtureof compounds containing 12 or 13 carbon atoms in the alkyl radical;

(b) from about 50% to 100% by weight of said ethoxylated alcohol mixtureof compounds containing 14 or 15 carbon atoms in the alkyl radical;

(c) from about 0% to 45% by weight of said ethoxylated alcohol mixtureof compounds containing 16 or 17 carbon atoms in the alkyl radical;

(d) from about 0% to 10% by weight of said ethoxylated alcohol mixtureof compounds containing 18 or 19 carbon atoms in the alkyl radical;

(e) from about 0% to 30% by weight of said ethoxylated alcohol mixtureof compounds having a degree of ethoxylation of zero;

(f) from about 45% to 95% by weight of said ethoxylated alcohol mixtureof compounds having a degree of ethoxylation of from 1 to 4;

(g) from about 5% to 25% by weight of said ethoxylated alcohol mixtureof compounds having a degree of ethoxylation of from 5 to 8; and

(h) from about 0% to 15% by weight of said ethoxylated alcohol mixtureof compounds having a degree of ethoxylation greater than 8.

A desirable component in an acid mix containing an alkyl ether sulfuricacid or other organic sulfuric or sulfonic acid is a viscosity reducingaid such as benzoic acid. The use of benzoic acid to reduce viscosity isdescribed in U.S. Pat. No. 3,957,671 issued May 18, 1976 to Sagel et alherein incorporated by reference. Preferably the weight ratio of thebenzoic acid to the organic sulfuric or sulfonic acid is from about 1:1to about 1:100.

Alpha-olefins having from 10 to 24 carbon atoms and fatty acids havingfrom 8 to 20 carbon atoms and the esters of fatty acids with 1 to 14carbon atoms in the alcohol radical may be converted to organic sulfuricor sulfonic acids and neutralized within the scope of the presentinvention. The acid mixes above, respectively, give upon sulfationalpha-olefin sulfonates, alpha-sulfocarboxylic acids, and estersthereof.

As used above, the esters of alpha-sulfocarboxylic acids are also knownas alpha-sulfocarboxylate alkylates. An additional material which may besulfonated and neutralized in the scope of the present invention areparaffin sulfonates having from 10 to 24 carbon atoms.

A preferred surfactant system and hence a preferred reaction masscomprises alkylbenzene sulfonate, alkyl sulfate, and alkyl ether sulfatein a respective weight ratio of about 0.5:1:2.0 to about 2.0:1:0.5. Theweight ratio of the organic sulfuric or sulfonic acid to the water inthe reaction mass is from about 2:1 to about 1:2, preferably about 10:16to about 1:1.

E. Neutralization Step

Detergent compositions are ordinarily sold as solid materials and assuch it is necessary to convert the organic sulfuric or sulfonic acid,which is a viscous liquid, into a fully or partially neutralized salt.The neutralization may be accomplished by suitable alkaline componentsas previously stated, which include sodium carbonate, sodium hydroxide,and the acid salts of carbonates such as bicarbonates andsesquicarbonates. The aforementioned components are merely those whichare conveniently used, and in fact, any sodium containing Lewis base maybe used. It is further noted that other non-sodium Lewis bases may beemployed with the sodium containing Lewis base. It is preferred asstated above, that the reaction mass in the claimed process shouldcontain the sodium sulfate at supersaturation following theneutralization step. This, or course, means that during the removal ofthermal energy following neutralization that the sodium sulfate will besupersaturated within the heat exchanger(s). The pH of the reaction massis conveniently from about 6 to about 12.

Subsequent to the neutralization process, the aqueous mixture containingthe neutralized organic sulfuric or sulfonic acid, the sodium sulfate,small amounts of the alkaline component, will be passed through one ormore heat exchangers to lower the temperature of the reaction mass alsoknown as the paste.

It is also often desirable to recirculate a portion of the neutralizedpaste. The unneutralized acid mix is added to the recirculating pastestream to dilute the acid mix and further control the temperature uponneutralization. This operation is known as paste recirculation andavoids diluting the acid mix with components which are undesirable inthe final product, e.g., water. The paste recirculation ratio is morepreferably greater than 5:1, and most preferably greater than 10:1 ofparts paste per part acid mix. The portion of the neutralized paste,which is not recycled, is drawn off for further processing into thedetergent composition.

It was noted above that any of several conventional heat exchangers maybe used with the present invention. Most commonly, however, the type ofheat exchanger which will be used in the present invention, is a largeconduit through which the aqueous mixture containing supersaturatedsodium sulfate passes, preferably with turbulence to facilitate mixing.Inside the large conduit are one or more smaller conduits through whichthe cooling medium flows. Suitable heat exchangers as previously statedare manufactured by American Standard of Buffalo, N.Y. 14240. Suchdevices are discussed in detail in American Standard Bulletin 104-24 5M7-72KC, herein incorporated by reference.

The most convenient cooling medium will of course be water at therequired temperature. However, any cooling medium any be used providedthat it can rapidly remove heat from the paste stream flowing throughthe larger conduit. It is preferred, but not necessary, that the flowrate of the cooling medium as it passes through the smaller conduit issufficient to accomplish turbulent flow to minimize the amount ofcoolant which is required per given quantity of paste. This minimizesnot only the amount of cooling medium which must be used, but also theamount of space which must be taken up within the larger conduit by thesmaller conduits containing the cooling medium. The walls of the smallerconduit by convention are constructed to rapidly transfer heat from thereaction mass to the cooling medium. The heat exchanger will be run suchthat the cooling medium therein is maintained between about 5° C. and100° C., preferably about 10° C. to about 70° C., more preferablybetween about 30° C. and about 65° C. As the object of utilizing theheat exchanger(s) is to remove thermal energy from the reaction mass, itis preferred that the temperature of the reaction mass, as it existsfrom the last heat exchanger in the series be in the range of about 100°C. to about 50° C., preferably about 95° C. to about 60° C.

F. Slurry Introduction

The present invention accomplishes the reduction of sodium sulfateprecipitation in the heat exchanger by, surprisingly enough, increasingthe amount of sodium sulfate within the heat exchanger. That is, it isnot the amount of sodium sulfate which is present in the heat exchangerbut rather the form of the sulfate which is important.

While not wishing to be bound by any particular theory, it is believedthat the discovery of the property of controlled crystal growth accountsfor the present invention. That is, as the sodium sulfate issupersaturated, almost any disturbance within the reaction mass willcause the sodium sulfate to precipitate out. Unfortunately, sodiumsulfate in its anhydrous form plates out on the surfaces within the heatexchanger. Eventually if nothing is done to counteract the plating out,the system will become completely plugged with the sodium sulfate. Ithas been discovered, however, that if a slurry of anhydrous sodiumsulfate is introduced into the aqueous mixture in the heat exchanger,that the system may be operated continuously without the need toshutdown the heat exchanger.

Thus, if a sufficient amount of a supersaturated anhydrous sodiumsulfate slurry is introduced into the aqueous mixture the precipitationof sodium sulfate on heat exchanger surfaces is diminished. Preferablythe weight ratio of the slurry to the aqueous mixture is from about 2:1to about 1:200. The anhydrous sodium sulfate in the slurry preferablyhave a particle size of 0.01 micron to 100 microns, more preferably 0.03micron to 20 microns. The anhydrous sodium sulfate is preferably presentin a ratio to the water in the slurry of from about 160:100 to about42:100. The slurry is introduced into the aqueous mixture by anyconvenient means. It is preferred that the slurry be introduced into therecirculation loop as previously described to give maximumeffectiveness. The slurry is conveniently delivered to the heatexchanger through the means described in U.S. Pat. Nos. 2,825,543 and2,987,380 issued Mar. 4, 1958 and June 6, 1961 to McCracken et al andBrumbaugh et al respectively, both of which are incorporated herein byreference.

It is believed that in the present system that by introducing the slurryof anhydrous sodium sulfate into the aqueous mixture that theprecipitating anhydrous sodium will not deposit onto the conduitcontaining the cooling medium. Rather, the sulfate in the slurry seedsthe precipitation of the sodium sulfate in the aqueous mixture and theprecipitated sodium sulfate is carried out of the heat exchanger withthe remainder of the reaction mass. The predominant salt which wouldotherwise precipitate is anhydrous sodium sulfate, thus the slurryaccomplishes homogeneous seeding in the aqueous mixture. The positiveeffect of the present invention is two-fold. First, the aqueous mixtureis run under conditions of supersaturation and second, the amount ofsodium sulfate is further increased by the introduction of the sulfatein the slurry. An additional benefit to using the anhydrous sodiumsulfate slurry is that it will function as a heat sink provided that thetemperature of the slurry is less than that of the aqueous mixture.

To maintain the maximum efficiency of the present system, as well as toensure that the maximum amount of sodium sulfate is in the end product,it is desirable that the weight ratio of the sodium sulfate to the waterin the paste or reaction mass within the heat exchanger should be fromabout 100:60, to about 42:100, most preferably from about 40:30 to about45:100. The water content is more fully defined as the total water freeor bound within the system.

The following are examples of the present invention:

EXAMPLE I

A detergent acid mix is prepared with oleum having an acid strength of106.75%. The acid mix with excess sulfuric acid present is thenneutralized with aqueous sodium hydroxide solution to give a paste(reaction mass) comprising in parts:

7.0--sodium dodecyl benzene sulfonate

5.5--sodium hexadecyl triethoxy sulfate

5.5--sodium tallow sulfate

12.0--sodium sulfate

23.0--water

trace--free sulfur trioxide

trace--free caustic

The paste which is at a temperature of about 65° C. is then introducedinto an American Standard SSCF two pass heat exchanger, model number06800. The paste flows through the heat exchanger under conditions ofturbulent flow.

An aqueous slurry of anhydrous sodium sulfate comprising 45 parts of thesalt to 100 parts water is introduced into the aqueous mixture (paste)in a ratio of the slurry to the aqueous mixture of 1:10.

The cooling medium in the heat exchanger is water which enters the heatexchanger at about 29° C. and exits at about 34° C. The velocity of thewater is such that turbulent flow occurs in the heat exchanger.

When operating under the conditions above the heat exchanger requiresonly routine maintenance. In contrast, an identical system operated atthe same cooling medium temperature range without the benefit of theslurry introduction into the aqueous mixture will lose substantial heattransfer and paste flow capability in about 1/2 hour and will require ashutdown to remove the accumulated sodium sulfate within about 3 hours.

EXAMPLE II

Example I is repeated using as parts of paste to be cooled

17--sodium dodecyl benzene sulfonate or

17--sodium tallow alcohol sulfate

14--sodium sulfate

22--water

trace--free sulfur trioxide

trace--free caustic

Substantially similar results to those of Example I are obtained.Further, similar results are obtained when the above example is modifiedto a surfactant system containing 18 parts, 16 of which are sodiumhexadecyl triethoxy sulfate and 2 parts tallow alcohol sulfate.

EXAMPLE III

Sulfuric acid which is 85% active (15% H₂ O) is completely neutralizedwith dry sodium hydroxide. The reaction mass is then passed through aheat exchanger as defined in Example I. A slurry of anhydrous sodiumsulfate as defined in Example I is introduced into the heat exchanger topromote crystal growth on the anhydrous sodium sulfate. The coolingmedium (water) in the heat exchanger is maintained at 38° C. and thereaction mass is cooled from 95° C. to 90° C. As a comparative examplethe same system without the slurry introduction becomes plugged withsodium sulfate.

What is claimed is:
 1. In the process of nuetralizing an organicsulfuric or sulfonic acid or mixtures thereof in the presence of excesssulf(on)ating agent the steps of:(a) reacting said organic sulfuric orsulfonic acid and excess sulf(on)ating agent with a sodium alkalinecomponent thereby forming a supersaturated solution with respect to thesodium sulfate formed during said reaction; and, (b) cooling thereaction mass formed in step (a) in a heat exchanger while introducinginto the reaction mass an amount of an aqueous slurry of anhydroussodium sulfate, said amount of sodium sulfate being sufficient to reducethe deposition of sodium sulfate on the surfaces of the heat exchanger.2. The process of claim 1 wherein the cooling medium is maintainedbetween 5° C. and 100° C.
 3. The process of claim 1 wherein the weightratio of the anhydrous sodium sulfate to the water in the aqueous slurryis from about 160:100 to about 42:100.
 4. The process of claim 1 whereinthe organic sulfuric or sulfonic acid is selected from the groupconsisting of alkylbenzene sulfonic acid, alkyl sulfuric acid, alkylether sulfuric acid, olefin sulfonic acid, alkyl sulfonic acid,alpha-sulfocarboxylic acid, alpha-sulfocarboxylic acid alkylates, andmixtures thereof.
 5. The process of claim 1 wherein the weight ratio ofthe aqueous slurry to the aqueous mixture is from about 2:1 to about1:200.
 6. The process of claim 1 wherein the reaction mass is furthercooled by one or more additional heat exchangers.
 7. The process ofclaim 1 wherein the cooling medium is water maintained at a temperatureof from about 10° C. to about 70° C.
 8. The process of claim 1 whereinthe aqueous mixture contains benzoic acid in an amount sufficient toreduce the viscosity of the aqueous mixture.
 9. The process of claim 8wherein the benzoic acid has an alkali metal cation and is present in aweight ratio to the organic sulfuric or sulfonic acid of from about 1:1to abut 1:100.
 10. The process of claim 1 wherein the reaction massformed in step (a) is cooled to from about 100° C. to about 50° C. bythe heat exchanger.
 11. The process of claim 4 wherein the organicsulfuric or sulfonic acid is selected from the group consisting ofalkylbenzene sulfuric acid, alkyl sulfuric acid, and alkyl ethersulfuric acid and mixtures thereof.
 12. The process of claim 11 whereinthe organic sulfuric or sulfonic acid is an alkylbenzene sulfonic acid.13. The process of claim 11 wherein the organic sulfuric or sulfonicacid is an alkyl sulfuric acid.
 14. The process of claim 11 wherein theorganic sulfuric or sulfonic acid is an alkyl ether sulfuric acid. 15.The process of claim 1 wherein the alkaline component is selected fromthe group consisting of the sodium hydroxide, sodium carbonate, sodiumbicarbonate, sodium sesquicarbonate and mixtures thereof.
 16. In theprocess of nuetralizing an organic sulfuric or sulfonic acid selectedfrom the group consisting of alkylbenzene sulfonic acids, alkyl sulfuricacids, and alkyl ether sulfuric acids and mixtures thereof in thepresence of excess sulf(on)ating agent, the steps of:(a) reacting theorganic sulfuric or sulfonic acid and excess sulf(on)ating agent with analkaline component selected from the group consisting of sodiumhydroxide, sodium carbonate, sodium bicarbonate, and sodiumsesquicarbonate and mixtures thereof, thereby forming a supersaturatedsolution with respect to the sodium sulfate formed during said reaction;and (b) cooling the reaction mass formed in step (a) in a heat exchangerwhile introducing into the reaction mass an amount of an aqueous slurryof anhydrous sodium sulfate, said amount of sodium sulfate beingsufficient to reduce the deposition of sodium sulfate on the surfaces ofthe heat exchanger.
 17. The process of claim 16 wherein the sodium saltof the organic sulfuric or sulfonic acid is an alkylbenzene sulfonicacid.
 18. The process of claim 16 wherein the sodium salt of the organicsulfuric or sulfonic acid is an alkyl sulfuric acid.
 19. The process ofclaim 16 wherein the sodium salt of the organic sulfuric or sulfonicacid is an alkyl ether sulfuric acid.
 20. The process of claim 16wherein the weight ratio of the anhydrous sodium sulfate to the water inthe aqueous slurry is from about 160:100 to about 42:100.
 21. Theprocess of claim 20 wherein the weight ratio of the aqueous slurry tothe aqueous mixture is from about 2:1 to about 1:200.
 22. The process ofclaim 21 wherein the sodium salt of the organic sulfuric or sulfonicacid is a mixture comprising the sodium salts of an alkylbenzenesulfonic acid, an alkyl sulfuric acid and an alkyl ether sulfuric acidpresent in a weight ratio of from about 0.5:1.0:2.0 to about 2.0:1.0:0.5and wherein the sodium salt of the organic sulfuric and sulfonic acid ispresent in a weight ratio to the water in the reaction mass of fromabout 10:16 to about 1:1 by weight.
 23. The process of claim 22 whereinthe temperature of the cooling medium is water maintained at from about5° C. to about 100° C.